Various design solutions exist for constructing elevator systems that optimize space while gaining cost and performance benefits. By conserving space, building complexity and costs are reduced. Various designs exist for elevator systems that eliminate the need for a machine room by housing most or all of the elevator components within the hoistway. Machines located within a hoistway are more readily accessible for servicing. In order to fit within a hoistway, various conventional elevator components must be eliminated or re-configured. Some existing designs provide for machines mounted along side an elevator car or counterweight travel path. Others provide for mounting a machine in a pit or overhead area of a hoistway. Each of these designs requires complexity and imposes space limitations.
High performance elevators require direct coupling between a motor and drive sheave in order to provide smooth, low vibration performance. The lack of a gearbox requires the machine to produce high torque at low operating speeds relative to industrial machines of the same power output rating. This results in motors that are large and expensive relative to industrial machines of the same power output. The size and cost of conventional high-performance gearless machines makes it impractical to implement them in rope-climbing elevator designs, which are desirable for various reasons including optimization of hoistway space and convenient accessibility. Geared machines are undesirable for certain applications such as rope-climbing systems because they introduce vibrations and inefficiencies.
It is therefore an object of the present invention to provide an elevator system that minimizes space requirements, eliminates the need for a machine room, and provides convenient access to machine components. It is a further object to provide an elevator machine that includes the output and low vibration benefits of a high performance machine, while providing a lightweight and efficiency benefits of a gearless machine. These and other objects are achieved by the invention described herein.
Among the ways to eliminate and reduce the size of elevator components is to replace hydraulic and geared elevator machines with gearless ones, enabling generally flatter profiles. The "flat" machines are more readily adapted for positioning within the hoistway and provide mechanical advantages over geared or linear induction motors. According to the present invention, an elevator system including a counterweight assembly having a plurality of flat drive machines enabling the counterweight assembly to climb a vertical rail in the hoistway is provided. The drive machines include permanent magnet motors and friction drive wheels for engaging the rail. The counterweight assembly is roped to n elevator car for corresponding vertical movement therewith.